Stucture And Photorefractive Properties In Mn, Mg Codoped LiNbO₃ Crystals With Varied Mn Concenttration

Mn:Mg:LiNbO₃ congruent Lithium Niobate single crystals were grown by the Czochralski method in the atmosphere environment, and the as-growth crystals have no macroscopic defects and have a perfect optical homogeneity. The optimum technological conditions for growing co-doped Mn:Mg:LiNbO₃ single crystals were also determined.By investigating the ultraviolet-visible absorption spectra and IR absorption spectra, the occupying mechanism of the dopants was studied. They showed that Mg doping concentration of 5mol.% isn't over the threshold; Mn ions entering LiNbO₃ crystal substitute Li⁺ sites; At the oxidation state, the growth state and the reduction state, the circumstance of the atom is different, so the absorption edge also varied.The results from the XRD experiment of the single crystals showed that the crystal's defect did not change much with the increase of Mn doping amount; The crystal with the same Mn doping amount, compared with the growth state, the defect increased at the oxidation state and decreased at the reduction state.Using two beam coupling experiment, the dependence of the diffraction efficiency and the response time of the co-doped Mn:Mg:LiNbO₃ crystals on the Mn concentration and the post treatment was studied systematically. The results indicated that the diffraction efficiency was very low when we doped 5mol.% MgO and a few MnO2; As for the same crystal, from oxidation state to grow state and to reduction state, its writing time was shortened and diffraction efficiency decreased; With the increase of Mn doping amount, the diffraction efficiency firstly decreased and then increased; Mg:Mn:LiNbO₃ congruent Lithium Niobate single crystals had the nonvolatile properties.The transmission facula distortion is directly observed to study the optical damage resistance of the co-doped Mn:Mg:LiNbO₃ crystals. The results showed that the crystal's optical damage resistance was very strong,no optical damage happened.The focused laser beam was applied for the first time to study the photorefractive properties. Higher diffraction efficiency was obtained, and the erase time was much longer than the write time. This meaned that the double-...